Burner control



O Umted States Patent [1113,548,872

[72] Inventor John James 11130 [56] References Cited Liverpool, EnglandUNITED STATES PATENTS P 862,867 8/1907 Eggleston 251/61.1UX [22] FiledSept. 19, 1968 2,953,151 9/1960 bnyder 137/593)( [45] Patented Dec. 22,1970 2,986,133 5/1961 Mattson 123/136 [731 3 173 447 3/1965 Lebow137/593 M" Eu a Brim 3,256,870 6/1966 Walker 123/136X [32] Priority g gfr gr m 3,336,012 8/1967 Walker l23/136X [33] GEE-film 3,374,777 3/1968Walker 123/136 [31] 42978/67 Primary Examiner-M. Cary Nelson AssistantExaminer-R. B. Rothman Attorney-Morrison, Kennedy & Campbell [54] g s gABSTRACT: The supply of liquid fuel to a burner, for exam- Figs ple in aglass melting tank, is controlled by apparatus including [52] U (l137/565, a shutoff valve in a fuel supply line, and a sealed chamber137/593 communicating with the supply line between the shutoff valve[51] 1nt.Cl. F2311 11/00 and the burner, which chamber has a flexiblewall portion [50] Field 01 Search 137/593, which enables the volume ofthe chamber to be varied when the shutoff valve is operated.

PATENTEDUEG22I97G 3548372 SHEET 1 [1F 2 lnvenlor MD K B Attorney 55 4 I54 n I 27 52 53 41 1 BURNER coN'rnor.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to apparatus for controlling the supply of liquid fuel toburners and, more especially, to apparatus for controlling high pressureliquid fuel supply to burners in industrial heat treatment processes.

2. Description of the Prior Art Liquid fuel burners are usedextensively-in industrial heat treatment processes. In, for example, thefiring of continuous glass melting tanks two banks of oil burners arelocated in opposite sidewalls of the glass tank and the'bumer banks areoperated alternately so that all the burners at one side of the tank areactivated for a period of about 20 minutes and are then extinguished andthen all the burners on the other side of the tank are activated for a20 minute period.

A serious difficulty exists when the fuel supply to a burner isdiscontinued by closing a shutoff valve in a fuel supply line to theburner, since the fuel in the supply line between the shutoff valve andthe burner will continue to flow through the burner after the shutoffvalve is closed, particularly if the fuel supply pressure is high. Thisis not detrimental to the operation of the process whilst atomizing airis maintained at full power and combustion air is also being supplied tothe burner. However, this fuel will in general leak from burner afterthe supply of combustion air to the burner has been discontinued andconsequently the leaking fuel burns with incomplete combustion,generating smoke. This is particularly undesirable where a glass tank isbeing fired as the interior of the tank can be clouded, adverselyaffecting material undergoing treatment in the tank.

To overcome this serious problem it is known to provide an expandablechamber in communication with the fuel supply line between the shutoffvalve and the burner. Such known expandable chambers comprise a cylinderhaving a piston slidably mounted therein, the piston being arranged tobe displaced, when the shutoff valve is closed, in a sense to expand thevolume of the cylinder in communication with the fuel supply line andthereby cause a rapid reduction in the fuel pressure in the supply line.Fuel is therefore sucked through thesupply line away from the burner,and leakage of fuel through the burner is avoided.

Such expandable volumes are effective in preventing fuel leakage after aburner has been shut off, but it is difficult to provide an adequate andlasting seal between the piston and its cylinder, particularly where thefuel supply pressure and temperature are relatively high.

An object of the present invention is to provide apparatus forcontrolling the supply of liquid fuel to a burner which is effective toprevent fuel leakage when the burner fuel supply is shut off and whichis devoid of moving seals.

SUMMARY According to the present invention apparatus for controlling thesupply of liquid fuel to a burner, comprises a fuel supply linecontaining a shutoff valve, a sealed chamber communicating with thesupply line between the shutoff valve and the burner, a flexible wallportion in said chamber, and control means operatively connected withthe shutoff valve and adapted to move said wall portion in. a sense toincrease automatically the volume of the chamber in communication withthe supply line when the shutoff valve is closed.

Preferably the control means are further operable to move the wallportion automatically in a sense to decrease the volume of the chamberin communication with the supply line when the shutoff valve isopened.

ln a preferred embodiment of the invention the flexible wall portioncomprises a first flexible diaphragm which divides a diaphragm vesselinto two chambers, which diaphragm is mechanically connected to a seconddiaphragm which divides a second vessel into two. chambers, one of thechambers defined by said first diaphragm communicates with the fuelsupply line, and the control means includes pressure fluid linesconnected to the other three chambers defined by the diaphragms, andvalve means connected to said pressure fluid lines and selectivelyoperable to supply pressure fluid controlling the movement of thediaphragms and hence the volume of the chamber communicating with thefuel supply line.

in another embodiment of the invention the flexible wall portioncomprises a collapsible bellows disposed in the chamber, the interior ofthe bellowsbeing sealed from that part of the chamber which is incommunication with the fuel supply line, the control means controllingthe pressure of fluid in a pressure fluid line communicating with theinterior of the bellows to control the expansion of the bellows andthereby the volume displaced by the bellows in said part of the chamber.When the shutoff valve is closed, the control means cause the bellows tocontract, increasing the volume of the chamber in communication with thefuel supply line, so that fuel is sucked from the supply line away fromthe burner and leakage of fuel is prevented. When the shutoff valve isopened to permit the flow of fuel to the burner the control means causethe bellows to expand to reduce the volume of the chamber incommunication with the supply line, and thus to prepare the chamber forthe next shutoff operation.

In another embodiment of the invention the sealed chamber is constitutedby the interior of a collapsible bellows, the control means controllingthe pressure of fluid in a pressure fluid line communicating with anenclosure surrounding said bellows so as to control the expansion andcontraction of the bellows and thereby the volume of the sealed chamber.When the shutoff valve is closed, the control means cause the bellows toexpand, and when the shutoff valve is opened the control means cause thebellows to contract.

Preferably expansion and contraction of the bellows is assisted by anactuator rod connected-to one end of the bellows. The actuator rod maybe movable by means of a doubleacting fluid-pressure operated piston,extension and retraction of which is controlled by said control means.

The control means preferably include a control valve operativelyconnected to the shutoff valve so that when the shutoff valve is openthe control valve is disposed in a first setting in which it connects apressure fluid source to said pressure fluid line so as to reduce thevolume of the chamber communicat ing with the fuel supply line and whenthe shutoff valve is closed the control valve is disposed in a secondsetting in which it connects an exhaust outlet with the said pressurefluid line to cause an increase in the volume of said chamber incommunication with said supply line.

ln the said one embodiment the said pressure fluid line alsocommunicates with the side of said piston remote from the bellows, saidpressure fluid line being connected selectively to the pressure fluidsource or to the exhaust outlet according as the control valve isdisposed in said first or said second setting respectively.

A common actuator may be provided for operating both the control valveand the shutoff valve. Preferably the control valve is operable by theactuator through a lost motion connection such that the control valve ismoved from its first into its second setting only when the shutoff valveis fully closed or substantially fully closed.

In one embodiment the control valve comprises a spool valve having alinearly displaceable valve member and the lost motion connectioncomprises a tappet arm attached to an actuator and engaging the valvemember only when the actuator approaches its position corresponding tothe shutoff valve being fully closed,

The invention also includes a liquid fuel burner provided with apparatusas hereinabove defined for controlling the supply of fuel thereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a purely diagrammaticpartial section through a burner fitted in a glass melting tank, andprovided with apparatus according to the invention, for controlling thesupply of liquid fuel to the burner, indicated schematically,

FIG. 2 shows diagrammatically the apparatus, partially in section, forcontrolling the fuel to the burner shown in FIG. 1, and

FIG. 3 is a section through a two-diaphragm device which constitutes amodification of the apparatus of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 a burner Bis supplied with fuel oil by way of a fuel supply line 11, and withatomizing air by way of an air supply line 12. The burner B is disposedcentrally in the outlet of a combustion air duct 13 which enters a sidewall of a glass melting tank.

A shutoff valve 14 is included in the fuel supply line 11. The valve 14has an actuating lever 15 (FIG. 2) which is slotted at 16 to receive asliding pin 17 provided at one end of a piston rod 18. The piston rod 18is connected to a piston 19 slidably mounted in a cylinder 20, so thatthe opening and closing of the shutoff valve 14 is dependent upon theposition of the piston 19 within cylinder 20. Thus retraction of thepiston 19 towards the right-hand end of the cylinder 20, as shown infull lines in FIG. 2, closes the valve 14 and extension of the piston 19towards the left-hand end of the cylinder 20, as shown in broken lines,opens the valve 14, permitting the supply of oil through the supply line11 to the burner B.

The cylinder 20 has two fluid supply lines 21 and 22 connected thereto,the line 21 communicating with the smaller area side of the piston 19and the line 22 communicating with the larger area side of the piston19. The fluid pressure lines 21 and 22 enter the cylinder 20 in theunswept end volumes thereof. Respective three-way valves 21a and 22a inthe lines 21 and 22 respectively have two respective positions in whichthey connect the respective lines 21 and 22 with a common fluid pressuresource P or with atmosphere respectively.

The piston rod 18 carries a tappet arm23 which, in the extreme retractedposition of the piston 19 (shown in full lines) corresponding to closureof the valve 14, engages operatively one end of a spool valve member 24,moving the latter slidably in a five-port valve housing against theaction of a thrust spring 25 engaging the other end of the spool valvemember 24.

The spool valve member 24, and the ports in the housing 25, are soarranged that, when the valve member 24 is moved by the arm 23 towardsthe right-hand end of the housing 25, a fluid pressure line 26 extendingfrom the source P is connected to a line 27, while a line 28 isconnected to an exhaust outlet 29. When the spool valve member 24 isreleased the spring 25' urgcs the member 24 towards the left-hand end ofthe housing 25, connecting the line 26 to the line 28 and connecting theline 27 to an exhaust outlet 30.

The line 28 is branched into two branch lines 28a, 28b. The branch line28a passes through a plate 31 which forms the base of a closed chamber32, the branch line 28a communicating with the interior of a bellows 33secured at its lower end to the base plate 31. At its upper end thebellows 33 carries a plate 34 which is connected to a piston rod 35. Thepiston rod 35 passes downwardly through a fluid seal 36 in base plate 31and is connected to a piston 37 which is slidably mounted in cylinder 38attached to the under surface of the plate 31. The branch line 28b opensinto the cylinder 38 beneath the piston 37 that is, on the larger areaside thereof, so that the cylinder chamber 32 externally of the bellows33 with the supply line 11 between the burner B and the shutoff valve14.

The operation of the apparatus will now be described.

To operate the burner B combustion air is first supplied to thecombustion region at a rate of about 500 cu. ft. per minute through theduct 13, and atomizing air is then supplied to the burner B at apressure in the region of p.s.i. through the supply line 12. The shutoffvalve 14 is then opened to admit fuel oil at a pressure of 60 p.s.i. tothe burner B through the supply line 11, the rate of flow of atomizingair to the burner B being about 80 cu. ft. per minute. I

The valve 14 is moved into and maintained in the open position byconnecting the line 21 to exhaust and the line 22 to the pressure sourceP, extending the piston 19 into and retaining it in its position at theleft of the cylinder 20 as shown in FIG. 1 in broken lines.The'tappet'arm'23 is out of contact with the spool valve member 24,which is urged towards the left-hand end of the housing 25 by the spring25' to connect the line 27 to the exhaust outlet 30 andthe line 28 tothe fluid pressure line 26. Pressure fluid is supplied to the largerarea side of the piston 37 by way of the branch line'28b and to theinterior of the bellows 33 by the branch line 28a, and the combinedupward fluid pressure extended on the piston 37 and the plate 34 of thebellows 33 causes the bellows 33 to rapidly expand. The volume of thechamber 32 communicating with the supply line 11 is therefore reduced toits minimum value.

To terminate operation of the burner B the settings of the valves 21aand 22a are reversed sothat'the line 22 is connected to exhaust andpressure fluid is supplied from the source P by way of the line 21 tothe left-hand side of the piston 19, thereby causing the latter toretract to the right to the position illustrated in FIG. 1 in fulllines. This retraction of the piston 19 is transmitted through pistonrod 18, the pin 17, and actuating member to the valve 14, closing thelatter and terminating the supply of fuel oil along the supply line 11to the burner B.

Near the end of the retracting movement of the piston 19 the tappet arm23 engages and depresses the spool valve member 24 against the action ofthe spring 25 moving the spool valve member 24 to the right-hand end ofthe housing 25. The line 27 is thereby connected to the pressure sourceP through the fluid pressure line26 and the line 28 is connected to theexhaust outlet 29. The interior of the bellows 33 and the larger areaside of the piston 37 are connected to exhaust (i.e. to atmosphere)whilst fluid under pressure is supplied to the cylinder 38 on thesmaller area side of the piston 37; this causes the bellows 33 tocontract rapidly, reducing the pressure in the chamber 32 and increasingrapidly the volume of the chamber 32 in communication with the supplyline 11, oil remaining in the line 11 is therefore sucked into thechamber 32, said oil flowing back along that part of the supply line 11between the line 39 and the burner B. Leakage of oil from the burner Bafter closure of the valve 14 is thereby eliminated.

The bellows 33 provide a rapid and effective means for increasing thevolume of the chamber 32 in communication with the supply line 11,without the necessity of sliding seals in the oil filled chamber 32. Theuse of a flexible or collapsible wall portion, such as the bellows 33,therefore gives the apparatus a longer effective service life than isobtainable with piston and similar devices requiring sliding seals.

It will be appreciated that'the present invention has been described byway of example only with reference to a specific embodiment and thatmany variations and modifications of the invention will be apparent topersons skilled in the art. Thus whilst the control means for thebellows 33 has been described as a fluid pressure system it will beapparent that other control systems, such, for example, as hydraulic orpneumatic systems, can be used. For example, the cylinder 20 traction ofthe bellows 33 being controlled as described above. In a furtheralternative the bellows 33 could be replaced by, for example, a flexiblediaphragm device.

A modification of the apparatus of FIGS. 1 and 2 is illustrated in FIG.3. Two identical diaphragmvessels 40 and 41 are secured to opposite endsof a frame 42. The vessel 40 comprises two cup shaped halves 43 and 44with a flexible diaphragm of an oil-resistant rubber peripherallyclamped between the two halves 43 and 44. A central bearing 46 integralwith half 44 forms the bearing for a diaphragm actuating rod 47 whoseupper end 48 is sealed into the center of the diaphragm. The lower end49 of the bearing 46 is reduced and screw cut, and this reduced end 49is fitted downwardly into a hole in the upper part of the frame 43 andis secured by anut 50 The second diaphragm vessel 41 is. identical withvessel 40 and comprises halves 51 and 52 between which a second flexiblediaphragm 53 is peripherally clamped. The upper half 52 has a centralintegral bearing 54 which is held in the lower part of the frame by anut 55. A diaphragm actuating rod 56 is slidably supported in boring thebearing 54, and the lower end of the rod 56 is sealed at 57 into thecenter of the diaphragm 53- The diaphragm actuating rods 47 and 56 arein axial align ment with each other towards one another within the frame42. The lower end of the rod 47 is screw cut with a left-hand thread,and the-upper end of the rod 18 is screw cut with a right-hand threadand the threaded ends of rods are connected by a turn buckle 58 so thatthe diaphragms 45 and 53 are mechanically connected for mutualdisplacement.

The upper sealed chamber of vessel 40 i.e. the chamber between the half43 and the diaphragm 45is connected by a line 59 to the fuel supply line11, andthe' lower chamber of vessel 40, i.e. the chamber between thehalf 44 and the diaphragm 45 is connected to the branch line 28a. Theupper chamber of a vessel 41, i.e. the chamber between the half 52 andthe diaphragm 53', is connected toline 27, and the lower chamber ofvessel 41 i.e. between the half 51 and the diaphragm 53 is connected tothe branch line 28b.

Branch lines 280 and 28b are connected to pressure line 28 as in FIG. 2which extends to the five port valve, and pressure line 27, also extendsto the five port valve of the control system. a

With the burner firing, air under pressure is supplied through the fiveport valve to the line 28 and from the line 28 the branches 28a and 28bso that the lower chambers of vessels 40 and 41 are connected to ahigh-pressure air source (about 60 p.s.i.), while the upper chamber invessel 41 is connected through line 27 to exhaust. The upper chamber ofvessel 40 is open to the fuel line 11; and in this position bothdiaphragms 45 and 53 are raised so that the upper chamber of vessel 40has a minimum volume.

When the burner stops firing andthe shutoff valve is closed to operatethe five port valve, the line 28 is connected to exhaust so that throughbranch lines 28a and 28b the lower chambers of both vessels 40 and 41are connected to exhaust, and air under pressure is supplied by line''27 to the upper chamber of vessel 41.-Because the shutoff valve isclosed the oil pressure in the chamber of vessel'40 is substantially atatmospheric pressure. The pressure of air in the upper chamber of vessel41 causesdownward displacement of diaphragm 53 which, through the'rod56, the turn buckle 58 and the rod 15, causes a simultaneous downwarddisplacement of the diaphragm 45 which increases to a maximum the volumeof the upper chamber of vessel 40. This causes any fuel oil in the line11 to be drawn into that sealed chamber.

Both the diaphragms 45 and 53 are made from a rubber which is capable ofwithstanding the high temperature, high pressure oil.

The burner control apparatus of the invention finds particularapplication in the control of banks of oil burners disposed in oppositesidewalls of a continuous glass melting tank. The banks of burners areoperated alternately for periods of about minutes each.

When the burners of one bank are being operated the combustion exhaustgases are drawn off from the tank down the combustion air supply ductsof the inactive burners and these hot gases are passed throughheat-retaining means, such as stacks of brickwork, which absorb heatfrom the exhaust gases passing therethrough and thus when the burnercycle is reversed and the opposite bank of burners is operated andcombustion air is drawn in through the said combustion air supply ducts,said combustion air is preheated by passage through the heatedheat-retaining means.

When the operation of a liquid fuel burner or a said bank of burners isto be terminated the following operations are effected in sequence:

1. The fuel supply to the burners is discontinued by closing a shutoffvalve in a fuel supply line connected to the burners;

2. The supply of atomising air to the burners, is reduced to about 25percent of its fully operational value; and,

3. The combustion air supply is terminated.

When the burners of one bank are inactive they lie in the path of theexhaust gases from the active bank of burners and a supply of atomizingair, at a reduced pressure, is maintained to the inactive burners toserve as a coolant and to prevent blocking of the inactive burners byforeign matter or soot carried in the exhaust gases from the activeburners.

When the burners of the inactive bank of burners are to be reactivatedthe supply of combustion air is first reinstated, then the supply ofatomizing air is increased to its full pressure and finally the shutoffvalve in the fuel supply line to the burners are opened.

I claim:

1. Apparatus for controlling the supply of liquid fuel to a burner, saidapparatus comprising a fuel supply line containing a shutoff valve, asealed chamber communicating with the supply line between the shutoffvalve and the burner, a flexible wall portion in said chamber, motivemeans operable selectively to move said wall portion in a sense toincrease the volume of said chamber and in the opposite sense todecrease the volume of said chamber, and control means for said motivemeans operative responsively to closing and opening of the shutoffvalve, said control means automatically causing said motive means tomove said wall portion in the sense to increase the volume of saidchamber when the shutoff valve is closed and in said opposite sensetodecrease the volume of said chamber when the shutoff valve is opened.

2. Apparatus as claimed in claim 1, wherein the flexible wall portioncomprises a first flexible diaphragm which divides a diaphragm vesselinto two chambers one of which chambers comprising the sealed chamberwhich communicates with the fuel supply line, the motive means comprisea mechanical connection between said first diaphragm and a seconddiaphragm which divides a second vessel into twochambers, and means tosupply pressure fluid in pressure fluid lines connected to the otherthree chambers defined by the diaphragms, and the control means comprisevalve means connected to said pressure fluid lines and selectivelyoperable to supply pressure fluid controlling the movement of thediaphragm and hence the volume of the sealed chamber.

3. Apparatus according to claim 2, in which said control means includesa control valve operatively connected to the shutoff valve so that whenthe shutoff valve is open the control valve is disposed in a firstsetting in which it connects a pres sure fluid source to said pressurefluid line so as to reduce the volume of the chamber communicating withthe fuel supply line and when the shutoff valve is closed the controlvalve is disposed in a second setting in which it connects an exhaustoutlet with the said pressure fluid line to cause an increase in thevolume of said chamber in communication with said supply line.

4. Apparatus according to claim 3, in which a common actuator isprovided for operating both the control valve and the shutoff valve.

5. Apparatus according to claim 4, in which the control valve isoperable by the actuator through a lost motion connection such that thecontrol valve is moved from its first into its second setting only whenthe shutoff valve is fully closed or substantially fully closed.

6. Apparatus according to claim 5, in which the control valve comprisesa spool valve having a linearly displaceable valve member and the lostmotion connection comprises a tappet arm attached to the actuator andengaging the valve member only when the actuator approaches its positioncorresponding to the shutoff valve being fully closed.

7. Apparatus according to claim l, in which the flexible wall portioncomprises a collapsible bellows disposed in the chamber, the interior ofthe bellows being sealed from that part of the chamber which is incommunication with the fuel supply line, the motive means comprise meansto supply pressure fluid in a pressure fluid line communicating with theinterior of the bellows, and the control means comprise valve meansconnected to said pressure fluid line and selectively operable to supplypressure fluid controlling the expansion and contraction of the bellowsand thereby the volume displaced by the bellows in said part of thechamber.

8. Apparatus according to claim 7, in which expansion and contraction ofthe bellows is assisted by an actuator rod connected to one end of thebellows.

9. Apparatus as claimed in claim 1, in which the sealed chamber isconstituted by the interior of a collapsible bellows, the motive meanscomprise means to supply pressure fluid in a pressure fluid linecommunicating with an enclosure surrounding said bellows, and thecontrol means comprise valve means connected to said pressure fluid lineand selectively operable to supply pressure fluid controlling theexpansion and contraction of the bellows and thereby the volume of thesealed chamber.

10. Apparatus according to claim 9, in which expansion and contractionof the bellows is assisted by an actuator rod connected to one end ofthe bellows.

11. Apparatus according to claim 10, in which the actuator rod ismovable by means of a double-acting fluid-pressure operated piston,extension and retraction of which is controlled by said control means.

12. Apparatus according to claim 11, in which the said pressure fluidline also communicates with the side of said piston remote from thebellows, and valve means associated with said pressure fluid line isoperable to connect said line selectively to a pressure fluid source orto an exhaust outlet.

13. A liquid fuel burner provided with control apparatus ac cording toclaim 1.

14. Apparatus according to claim 1, wherein said motive means comprisefluid pressure means to cause movement of said flexible wall portion inboth senses, and said control means comprise valve means whose settingcontrols the fluid pressure means of said motive means and is changedresponsively to closing and opening of said shutoff valve.

15. Apparatus according to claim 1, wherein said motive means comprisean actuator rod connected to a surface of said flexible wall portion ofsaid sealed chamber which surface is an external surface with respect tosaid sealed chamber, and a double-acting fluid-pressure operated pistonfor moving the actuator rod and thereby the flexible wall portion inboth senses, extension and retraction of the piston being controlled bysaid control means.

16. Apparatus according to claim 15, wherein said control means comprisevalve means whose setting controls the pressure of fluid delivered tosaid piston and is changed responsively to closing and opening of saidshut-off valve.

